1. Field of the Invention
The present invention relates to a cylinder type hydraulic clamp which is adapted to drive a clamping means by means of a hydraulic cylinder and, more particularly, to a hydraulic clamp of such a type that a leading end portion of a piston rod projected from a cylinder body is provided with a clamping means and a member to be clamped is adapted to be fixedly pressed between the cylinder body and the clamping means by hydraulically driving the clamping means toward the cylinder body under such a condition that the clamping means is advanced in a radial direction from the periphery of the piston rod.
2. Background of the Prior Art
A cylinder type hydraulic clamp, conventionally known the one shown in Japanese Provisional Utility Model Publication No. 1981-23,223 which is previously proposed by the inventor of the present invention.
As shown in FIGS. 15 and 16 (for a first conventional embodiment) and in FIG. 17 (for a second conventional embodiment hereof), the basic known constructions are as follows.
In a hydraulic cylinder 151 fixedly secured to a fixed member A is disposed in an upwardly facing manner so that a piston rod 152 projects upwardly, the upper portion 155 of the piston rod 152 which projects upwardly through the upper end wall 154 of the cylinder body 153 is equipped with a clamping means 156. The clamping means 156 is adapted to be pushed down through the piston 158 and the piston rod 152 by an oil pressure force of a pressure oil to be supplied to a clamp actuation oil chamber 157 within the cylinder body 153 so that a member B to be clamped which is externally fitted to the piston rod 152 can be fixedly pressed from its upper side by the clamping means 16 between the cylinder body 153 and the clamping means 156.
In this basic construction, when the member B to be clamped is externally fitted for its setting to the piston rod 152 from its upper side, it is necessary to prevent the clamping means 156 from projecting radially from the periphery of the piston rod 152 so as not to obstruct the setting. On the other hand, when clamping the member B to be clamped which has been settled onto the piston rod 152, it is necessary to project the clamping means 156 in the radial direction from the periphery of the piston rod 152.
The constructions of the portions for projecting or retracting the clamping means 156 in the radial direction, with respect to the periphery of the piston rod 152 in this way are as follows in the respective conventional embodiments.